The present invention is directed to a sleeve for a medical instrument, such as a dental instrument, said sleeve having a curvature and having both an outside shape in cross section and an outside diameter which deviate from a shape with a rotational symmetry. The invention is also directed to a method of forming the sleeve from a material suitable for super-plastic deformation.
Whether for reasons of functions or manipulations, or for the reasons of design, medical instruments, particularly instruments for dental medicine such as drilling, grinding, spraying or similar handpieces, require a shape that can deviate greatly from a cylindrical form under certain conditions. Thus, dental turbine handpieces or what are referred to as hand-and-angle pieces are usually fashioned greatly tapered toward the tool end. Over and above this, the handpieces often do not have a rotational symmetry and comprise what is referred to as a counter-bend in the gripping region. The outside contour of such a bend has been previously achieved, either in that two or more rotational symmetrical sleeves are joined to one another at the desired angle, such as disclosed by U.S. Pat. No. 4,007,529, with the two parts being connected such as by being screwed together or in that the desired bend contour has been milled out of the full form, for example out of a sleeve having a corresponding great wall thickness, such as disclosed by U.S. Pat. No. 4,332,562. This latter method of manufacture is, in fact, relatively intensive in material use, however, it has the advantage that the sleeve need not be divided into two members in the region of the location for the bend and the bend can be designed with a softer overall curvature and, thus, an overall contour of the handpiece can be more harmonically designed.
Other known methods employed in turbine handpieces for bending a cylindrical tube, which remains constant in diameter in accordance with the desired bend, is only suitable for those instruments in which the interior need not accept any parts, such as drive shafts and their bearings effected with fits or, respectively, tolerances on the inside. In addition, graduations in the outside diameter are only possible by joining tubes having different diameters or on the basis of the milling from the full form cited hereinabove.
In instruments that do not have a rotational symmetrical contour, for example in spray handles, it has been known to manufacture the grip sleeve from two half-shells, which will be formed by a longitudinal division of the sleeve. These half-shells are manufactured in accordance with a deep-drawing or stamping process. Such a sleeve produced in accordance with the deep-drawing or stamping process only allows simple contours to be provided but, by contrast, does not allow any contours having pronounced outside edges or changes in the outside surface. Added thereto is the fact that the manufacturing outlay is relatively high in order to obtain exact fitting half-shells. As a consequence of the high mold pressures, the apparatus outlay is comparatively high. Furthermore, additional calibration devices are required.